1. Field of the Invention
Embodiments of the present invention generally relate to non-linear fibers resistant to perturbations. More specifically, embodiments of the present invention relate to a fiber design that achieves high nonlinearity and a low sensitivity to perturbations in fiber scaling.
2. Description of the Related Art
Nonlinear optical devices are useful in numerous applications, including wavelength conversion, signal regeneration, spectral inversion, and low-noise amplification. These applications are often based on a parametric amplification process. Generally, the overall performance of a nonlinear device is closely related to the properties of the waveguide therein. For most applications, silica-based fibers offer the best properties, largely based on the balance between loss and nonlinearity offered thereby, of any available waveguide platform. However, because the nonlinearity of silica is low, the fiber length must be quite long (typical in the range 50-1000 meter or even longer) in many cases to allow significant nonlinear effects to accumulate at reasonable optical power. For numerous applications, such excessive length may lead to undesirable optical effects downstream.
For parametric amplification applications, a fiber must satisfy phase-matching conditions relating to the effective index values at the interacting optical wavelengths. It has recently been shown that there is significant variation in the effective index of guided light over the length of the fiber, and that variation of the effective index can cause significant degradation of phase matching over long lengths of fiber. As such, there is a significant design problem to achieve several fiber mode properties simultaneously. Some of these most relevant properties include: high nonlinearity, so that the length of fiber and/or input power can be reduced; an effective refractive index versus wavelength balance that allows phase matching of the desired nonlinear process in an unperturbed fiber; and low sensitivity of the phase matching to variations along the fiber length, i.e., scaling. This problem is especially difficult because existing fiber designs which achieve high nonlinearity are particularly sensitive to perturbations in core index or diameter.
Thus, there is a need for a non-linear fiber having high non-linearity, a good balance between effective refractive index and wavelength, and low sensitivity/high resistivity to perturbations.